﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;

namespace Movi.Extension
{
    /// <summary>
    /// 动态查询扩展
    /// </summary>
    public static class PredicateExtension
    {
        public static Expression<Func<T, bool>> True<T>() { return f => true; }

        public static Expression<Func<T, bool>> False<T>() { return f => false; }

        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expression1,
                Expression<Func<T, bool>> expression2)
        {
            var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast<Expression>());

            return Expression.Lambda<Func<T, bool>>(Expression.Or(expression1.Body, invokedExpression),
               expression1.Parameters);
        }

        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expression1,
                Expression<Func<T, bool>> expression2)
        {
            var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast<Expression>());

            return Expression.Lambda<Func<T, bool>>(Expression.And(expression1.Body,
              invokedExpression), expression1.Parameters);
        }
    }
}
